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FireWire in the automobile market

Posted: 16 Jul 2004 ?? ?Print Version ?Bookmark and Share

Keywords:firewire? aumtomobile? can? controller? bus?

Although the controller area network dominates the current automobile market, other bus systems are being increasingly used in this market to respond to data transmission requirements, reliability and customers' needs.

The first cars that support "real-time multimedia" applications according to the FireWire Standard are expected to enter the market in 2005. Families on their Sunday outings will then no longer have to endure the eternal question "Are we nearly there yet?" from their children. Thanks to the simple, economical use of video games and audio signals which the family is accustomed to at home, the question is more likely to be: "Oh, are we there already?"

The driver is provided with customized information, entertainment, communication and Internet access via the FireWire bus. The need for data transmission requires this type of multimedia bus to provide a speed of at least 400Mbps. World-wide standardization groups are working on a common high-speed bus of this type for the automobile industry as a whole. The ERTICO group in Europe, EpoC in Japan, AMI-C (Automotive Multimedia Interface Collaboration) and the IDB Forum (Intelligent Data Bus) are comparing different concepts and establishing specifications to develop a unified and economical solution.

Overview of FireWire

1394 is an IEEE standard for a serial high-speed bus. This serial bus defines the backplane physical layer (PHY) and the point-to-point virtual bus connected with cables. The current specifications IEEE1394-1995 and IEEE1394a-2000 support data rates of 100Mbps, 200Mbps and 400Mbps. The IEEE1394b specification extends this to 1.6Gbps and adds the architecture and infrastructure up to 3.2Gbps.

The IEEE1394b specification also allows for the use of optical transmissions including plastic optical fiber (POF) and extends the transmission path to 100m.

In comparison with many other buses, IEEE1394 is an open standard. In addition to the 1394 Trade Association, many other committees have worked together on this standardization, including Digital Video Broadcast (DVB), Digital Audio Video Council (DAVIC) and VESA Home Networking.

IDB-1394, the automotive FireWire specification, aims to achieve transmission paths of up to 18m and data rates of 100Mbps for POF or copper cables.

The general network architecture is divided into two groups. The onboard network links together all the multimedia components within the vehicle. The network connection node designed to connect external consumer devices is separate from an electrical point of view.

In comparison with the ring structure used for example with the MOST multimedia bus, the tree structure of 1394 has the following advantages:

??? Simple expandability - Devices can be easily added without having to break the existing network.

??? Fault tolerance and insulation - Faults can be easily located and the bus can continue to function even if a node is defective.

??? Plug and play - Devices can easily be connected or removed during operations without affecting the operation of other systems. As well as facilitating playing, this is also particularly important for the use of maintenance and analysis devices during servicing or in the workshop.

??? Upgrade mix - Devices that operate with higher speeds can easily be connected if they are available, as 1394 always guarantees backward compatibility. Each node dynamically alters its data rate depending on the speed supported by the end device. This means that external consumer devices can easily be connected to the automobile network even five years after a vehicle has been delivered.

A maximum of 63 devices can be connected to a network, the specification within 1394 allows up to 1,023 networks to be addressed and the memory capacity per node can support up to 281TB. These quantities will be sufficient for automobile applications over the coming years.

EMI is an important development element in automobile applications. The high data rates of 1394 contribute to the emission of energy which can influence other systems. An important aspect in this context is the selection of connectors and conducting media.

An additional PHY mode was introduced with the 1394b which is known as the "beta mode" and represents a modification of IBM's 8bit/10bit coding. Fibre Channel and Gigabit Ethernet use the same coding which lumps together and then decodes the data and control signals. This creates a robust system which fulfils and exceeds the strict energy emission requirements of FCC and other national standard and regulatory authorities.

In spite of these structural improvements, the question of whether a 1394 network based on copper connections can offer the same EMI performance as a system based on optical transmission remains open. However, possible long-term problems with POF cables are currently inspiring many users to reconsider copper cables as a transport medium.

The automobile industry

Carmakers and leading system providers have been creating a whole range of network-compatible electronic devices since the 1990s. Nowadays, most vehicles have at least a few networked microprocessor-based systems and the numbers are growing every year.

Market observers estimate that the average number of networked devices in the automobile industry will easily increase tenfold. For example, the Mercedes-Benz C class currently possesses up to 40 networked subsystems depending on the model. The cost of this type of implementation has fallen dramatically in line with the standard life cycle curve of semiconductors.

The main advantage of FireWire is its widespread use in consumer devices in the audio/video market. 1394 will become the essential multimedia standard in the daily life of car drivers when TV companies convert to digital transmission. This aspect is encouraging automobile manufacturers and providers to start considering the use of FireWire in the automobile market.

- Uwe Fuhrmann

European Market Development Manager, High-volume Analog and Logic

Texas Instruments Inc.

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